When conveying heterogeneous mixtures essentially containing different barely miscible liquid phases, it is often important to know with accuracy the percentage of each phase in the mixture. Moreover when such mixtures flow through pipes at a high rate, it is often of interest to follow in a continuous manner the variation of these contents versus time.
Thus, for example, when loading and unloading a tanker ship, a storage tank, etc., it is important to know the insoluble water content of the crude oil, or of the flowing valuable product.
At the present time, there does not exist any apparatus enabling such measurement in a precise and reliable manner. For example, regarding the "water+sediment" content of a crude oil, a conventional standard recommends collecting a single 100 cc sample for an entire shipload and analyzing this sample by centrifugation.
This yields only an extremely inaccurate, or even uncertain picture of the actual composition of the whole shipload, since due to the specific gravity differences of the phases, such a shipload is far from being homogeneous. In particular, it is possible to collect samples containing nearly no water when drawing off the upper layers of a product which is lighter than water, or, conversely, to collect only water when withdrawing the lower layer.
Apparatuses already exist for measuring the composition of a flowing medium, but such apparatuses either do not permit determination of the free water content of the medium (as is the case with apparatuses measuring electric conductivity), or do not provide for a precise and continuous determination (in the case of distillation apparatuses).
Microsensors determining a effective permittivity of the heterogeneous mixture can hardly be used when the mixture is a crude oil due to its viscosity. Moreover, a water or oil drop clogging the microsensor may affect all the measurements.